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      <title>如何优化 Dubbo 的性能？ - 交互式测验</title>
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        .option-item:hover {
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          align-items: center;
          min-height: 65px; /* Reserve space */
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        .nav-btn {
          background-color: #4a90e2;
          color: white;
          border: none;
          border-radius: 8px;
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          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
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            background-color: #28a745;
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        .nav-btn:hover {
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        .source-text {
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        .final-score-container {
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        .final-score-container h2 {
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            gap: 20px;
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            padding: 20px;
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        }
      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>如何优化 Dubbo 的性能？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，在Dubbo中合理配置线程池（Executor）的主要目的是什么？",
    "options": [
      "为异步调用提供必要的线程资源。",
      "实现服务调用的熔断与降级。",
      "避免因线程过多或过少导致的性能问题。",
      "减少网络传输中的数据序列化开销。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，合理设置线程池的核心线程数和最大线程数，是为了避免线程资源管理不当（过多或过少）而引发的性能瓶颈。虽然线程池是异步调用的基础，但其配置优化的核心目标是性能调优。",
    "source": "文档中「1.1 调整线程池配置」部分",
    "hint": "思考一下为什么我们需要“合理设置”线程池的大小，而不是简单地开启它。"
  },
  {
    "question": "在Dubbo的代码优化中，当遇到一个耗时较长的操作时，文档推荐采用哪种方式来避免阻塞主调用线程？",
    "options": [
      "增加服务提供者的`timeout`超时时间。",
      "使用Dubbo提供的异步调用方式。",
      "配置更高效的序列化框架如Hessian2。",
      "将服务拆分成更多个同步调用的微服务。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "对于耗时操作，文档推荐使用Dubbo的异步调用功能（例如返回`Future`对象）。这样可以将耗时任务交由其他线程处理，主线程不必等待结果返回，从而避免了阻塞，提高了系统的吞吐能力。",
    "source": "文档中「2.2 异步处理」部分",
    "hint": "文档中提到了一个与 `Future` 对象相关的调用方式，专门用于处理耗时操作。"
  },
  {
    "question": "在“服务治理”章节中，配置`loadbalance=\"roundrobin\"`这样的负载均衡策略，其主要作用是什么？",
    "options": [
      "在服务调用失败时，自动切换到另一台可用的服务提供者。",
      "将客户端请求均匀地分发到多个服务提供者，以均衡负载。",
      "启用分布式追踪，监控请求在系统中的完整链路。",
      "当某个服务出现故障时，快速失败并返回错误，避免资源占用。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "负载均衡策略的核心目标是将进入的请求根据特定规则（如轮询、加权轮询等）分发到后端的多个服务实例上，从而避免单一实例负载过高，提高整个集群的吞吐量和响应速度。",
    "source": "文档中「4.1 实现负载均衡」部分",
    "hint": "“负载均衡”这个词本身就暗示了它的主要功能是关于如何分配“负载”。"
  },
  {
    "question": "根据“网络优化”部分的建议，以下哪项是减少网络请求次数的有效策略？",
    "options": [
      "将多个独立的请求合并成一个批量请求进行发送。",
      "使用Netty作为底层的高效传输协议。",
      "为服务调用设置更短的超时时间。",
      "增加服务调用的重试次数（retries）。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "文档在“减少网络请求”小节中明确提出了两种方法：批量请求和本地缓存。将多个请求合并为一次网络调用，可以显著减少网络交互的次数，降低网络延迟和开销，从而提升性能。",
    "source": "文档中「3.2 减少网络请求」部分",
    "hint": "思考一下，除了让单次请求更快之外，还有什么方法可以优化整体的网络交互效率。"
  },
  {
    "question": "为了提高系统的稳定性和容错能力，文档在“配置容错机制”部分提到了哪些具体的配置项？",
    "options": [
      "配置`serialization=\"hessian2\"`和`codec=\"dubbo\"`。",
      "使用Prometheus和Grafana等监控工具。",
      "配置重试次数（retries）和失败转移（failover）。",
      "调整`coreSize`和`maximumSize`来优化线程池。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档通过XML配置示例 `<dubbo:reference id=\"userService\" retries=\"2\" failover=\"true\"/>` 展示了容错机制的具体实现。`retries`定义了失败后的重试次数，而`failover`（失败转移）是集群容错的一种策略，当调用失败时会自动切换到其他服务器。",
    "source": "文档中「4.2 配置容错机制」部分",
    "hint": "在服务治理部分，有一个XML代码示例直接展示了如何配置来应对服务调用失败的情况。"
  },
  {
    "question": "当需要分析一个请求在多个微服务之间的完整调用链路，以定位性能瓶颈时，文档推荐使用哪一类工具？",
    "options": [
      "代码剖析工具，如JProfiler。",
      "性能监控工具，如Prometheus。",
      "分布式追踪工具，如Zipkin或Jaeger。",
      "负载测试工具，如JMeter。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确区分了不同工具的用途。对于追踪请求的完整链路、分析跨服务调用的耗时和瓶颈，应使用分布式追踪工具（如Zipkin、Jaeger）。而Prometheus主要用于聚合性能指标，JProfiler则用于单个应用内部的代码级性能分析。",
    "source": "文档中「5.1 使用监控工具」部分",
    "hint": "文档中有一个术语专门描述“追踪请求的完整链路”这一功能。"
  },
  {
    "question": "在“代码优化”章节中，除了建议使用缓存和避免复杂逻辑外，还提到了哪种方法来减少CPU开销？",
    "options": [
      "保持Dubbo框架为最新版本。",
      "使用高效的序列化框架以降低序列化/反序列化开销。",
      "配置合理的`timeout`值以避免资源浪费。",
      "将多个请求合并为批量请求。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档在“优化服务实现”小节中指出，应“减少序列化开销：使用高效的序列化框架，减少对象序列化和反序列化的开销”。这是一个重要的代码层面优化，因为它直接影响到数据在网络传输前后的CPU处理效率。",
    "source": "文档中「2.1 优化服务实现」部分",
    "hint": "在服务调用时，对象需要被转换成二进制流才能在网络上传输，这个转换过程本身也存在性能优化的空间。"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
        // 存储每个问题的回答状态
        const userAnswers = new Array(quizData.length).fill(null); 

        const questionTextEl = document.getElementById('question-text');
        const optionsListEl = document.getElementById('options-list');
        const resultContainerEl = document.getElementById('result-container');
        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

        function loadQuestion() {
          resultContainerEl.innerHTML = '';
          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
          if (currentQuestionIndex >= quizData.length) {
            showFinalScore();
            return;
          }

          updateProgress();

          const currentQuestion = quizData[currentQuestionIndex];
          questionTextEl.textContent = `(${currentQuestionIndex + 1}/${quizData.length}) ${currentQuestion.question}`;
          
          currentQuestion.options.forEach((optionText, index) => {
            const li = document.createElement('li');
            li.className = 'option-item';
            li.textContent = optionText;
            li.dataset.index = index; // Store index in a data attribute
            // 如果这道题已经回答过，恢复状态
            if (userAnswers[currentQuestionIndex] !== null) {
                if (index === userAnswers[currentQuestionIndex]) {
                    li.classList.add('selected');
                }
            }
            optionsListEl.appendChild(li);
          });

          // 如果已经回答过，直接显示结果
          if (userAnswers[currentQuestionIndex] !== null) {
              const isCorrect = userAnswers[currentQuestionIndex] === currentQuestion.correctAnswerIndex;
              showResult(isCorrect, currentQuestion);
          }
          
          updateNavigationButtons();
          updateProgress();
        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
            score = userAnswers.reduce((acc, answer, index) => {
                return answer === quizData[index].correctAnswerIndex ? acc + 1 : acc;
            }, 0);

            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
        }
        
        function updateProgress() {
            const answeredQuestions = userAnswers.filter(answer => answer !== null).length;
            const progressPercentage = (answeredQuestions / quizData.length) * 100;
            progressIndicatorEl.style.width = `${progressPercentage}%`;
        }
        
        function updateNavigationButtons() {
            prevBtn.style.display = 'block';
            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  